644024557 has 6 divisors (see below), whose sum is σ = 707894894. Its totient is φ = 585476760.

The previous prime is 644024531. The next prime is 644024561. The reversal of 644024557 is 755420446.

It can be written as a sum of positive squares in only one way, i.e., 632321316 + 11703241 = 25146^2 + 3421^2 .

It is a de Polignac number, because none of the positive numbers 2^k-644024557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644024527) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2661138 + ... + 2661379.

Almost surely, 2^644024557 is an apocalyptic number.

It is an amenable number.

644024557 is a deficient number, since it is larger than the sum of its proper divisors (63870337).

644024557 is a wasteful number, since it uses less digits than its factorization.

644024557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5322539 (or 5322528 counting only the distinct ones).

The product of its (nonzero) digits is 134400, while the sum is 37.

The square root of 644024557 is about 25377.6389169678. The cubic root of 644024557 is about 863.5764872001.

The spelling of 644024557 in words is "six hundred forty-four million, twenty-four thousand, five hundred fifty-seven".